Rotary digging and compression enlarging driller and boring method

A compression enlarging driller comprises a vehicle body; a pole; an outer drilling rod; an inner drilling rod disposed within the outer drilling rod and moveable in a longitudinal direction; a windlass; a connecting lever having an upper end connected with a lower end of the inner drilling rod; a rotary digging bucket connected with a lower end of the connecting lever; a rotary enlarging device; a driving device; and a first hydraulic cylinder. When the driller bores a hoe, it can bore and enlarge the hole without changing a drill bit. A pile constructed by the driller has a high bearing capacity, the number of required piles is decreased, costs lower, and efficiency is improved.